Astronomers have discovered a strange new kind of star known as an "old smoker" after a 10-year study of the night sky.

These old big stars, which were once concealed, are found close to the Milky Way galaxy's centre. Astronomers believe the stars, which go dormant for decades and eventually become nearly undetectable before ejecting clouds of dust and smoke, may be involved in the distribution of elements throughout the cosmos, according to CNN.

The observations were described in four publications that were published in the Monthly Notices of the Royal Astronomical Society on January 25.

During the scan, which required tracking almost a billion stars in infrared light — which is invisible to the human eye — astronomers saw the old smoking stars for the first time.

The Visible and Infrared Survey Telescope at Cerro Paranal Observatory, which is perched high in the Chilean Andes, was used to conduct the observations.

The team's first objective was to look for young stars, which are difficult to find in the Milky Way due to their obscuration by gas and dust. However, because the galaxy has a high dust content, infrared light can see through it to identify otherwise faint or obscured objects.

According to Philip Lucas, an astronomy professor at the University of Hertfordshire, the team employed the Very Large Telescope of the European Southern Observatory to analyse individual stars because two-thirds of the stars were simple to identify and the remaining ones were more challenging. Lucas co-authored three studies in addition to being the lead author on one.

Out of the hundreds of millions of stars that astronomers observed, 222 showed discernible variations in brightness. The group discovered that 32 of them were young stars, with luminosities increasing by at least 40 times and sometimes up to 300 times. Since many of the eruptions are still occurring, astronomers can keep track of how the stars change over time.

“Our main aim was to find rarely-seen newborn stars, also called protostars, while they are undergoing a great outburst that can last for months, years, or even decades,” said Dr Zhen Guo, Fondecyt Postdoc Fellow at the University of Valparaiso in Chile, in a statement. Guo was the lead author of two studies, and coauthor on the other two.